[BUG] x86: reboot doesn't reboot

From: Steven Rostedt
Date: Thu Apr 03 2014 - 02:14:30 EST

I noticed that one of my test boxes no longer does a reboot with the
latest kernel. It goes down and shows:

[ 51.589896] reboot: Restarting system
[ 51.593567] reboot: machine restart

And the system sounds like it turns off (the fans stop), but then I
just sit there and wait, and wait and wait. The system never starts up

I did a bisect and it landed on: a4f1987e4c54 "x86, reboot: Add EFI and
CF9 reboot methods into the default list" which looks like a very
likely suspect. I removed that and fb3bd7b19b2b, as the second commit
was just a fix up of the first, recompiled, installed and rebooted to
that kernel. I tried to reboot again and sure enough after posting the
"machine restart" I started getting those "Press any key to continue."
messages again. That's a good sign.

Linus mentioned to me to use "reboot=pci" on the kernel command line,
but no dice. That doesn't seem to make a difference.

I see in the merge commit:

Pull x86 reboot changes from Ingo Molnar:
"Refine the reboot logic around the CF9 and EFI reboot methods, to make
it more robust. The expectation is for no working system to break,
and for a couple of reboot-force systems to start rebooting
automatically again"

Unfortunately, the expectation of no working system to break, didn't
quite stand up to expectations :-/

-- Steve
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